The effect of oxidation and acidification on the speciation of heavy metals in sulfide-rich freshwater sediments using a sequential extraction procedure

The speciation of metals in a contaminated, anoxic, sulfide-rich, freshwate r sediment was determined experimentally, using a sequential extraction pro cedure based on the method of Tessier et al. Taking into account the advant ages and disadvantages of sequential extractions, the applied methodology a llowed the investigation of the influence of aeration and acidification on the distribution of various metals in the sediment. Aeration caused Zn and Cd to be released from sulfides. Carbonates were partly dissolved by the ox idation process, causing mobilisation of Ca. Fe became less mobile owing to a stronger binding to organic matter. The speciation of K, Al, Ni, Pb and Mn and to a lesser extent of Cu was not affected by aeration. As a result o f acidification of the aerated sediment, Ca, Mn, Ni, Zn and Cd became more mobile owing to the dissolution of carbonates.